Abstract: To reduce signal wires of a cooling system of a computer, thereby providing a small cooling system. The cooling system for a computer of the present invention comprises a temperature sensor for measuring the temperature inside a computer; an SM bus controller for setting up prescribed temperatures and register values corresponding those temperatures, for reading out through an SM bus, and for notifying through another SM bus a fan rotation speed control IC of the register value corresponding the measured inside temperature; and the fan rotation speed control IC for supplying a cooling fan with a reference voltage defined by a reference voltage signal corresponding to a register value notified by the SM bus controller through the SM bus. Here, the fan rotation speed control IC sets up register values and reference voltage signal corresponding to the register values.